This invention relates to an adapter and tooth tip assembly which is adapted to be mounted on a lip of a dipper bucket. The tip is retained on the adapter by the adapter-tip interface and by a drive through pin.
A plurality of adapter-tip assemblies are mounted on the lip of a dipper bucket to scrape and dig material which goes into the bucket. Each adapter is rigidly affixed to the lip by one of several well-known means, including a C-clamp and wedge arrangement. The nose of an adapter projects beyond the lip and is received in the socket of a removable tooth tip.
During operation of a dipper bucket, the outermost or front end of a tip is abraded while digging and scraping material. In addition, the tip is subjected to bending stresses. In order to prevent failure or breakage of the tip, the wall at the rear of the tip between the outside surface of the tip and the adapter receiving socket must be of sufficient thickness to resist the stresses. A problem with a tip which has a high maximum stress for a given load is that this wall thickness must be increased. Since the allowable weight of a tip is limited in order to enable handling by one man, it is advantageous to have as low a maximum stress as possible to permit a thinner wall section at the rear and a heavier spade section at the front to prolong the useful life of the tip. This increases the tonnage of material dug before a tip is replaced and reduces the weight of the material remaining in a tip when it is replaced.
The front of a tip used on a dipper bucket has a flat, spade-like shape for optimum digging efficiency. In other words, when a dipper bucket having a plurality of adapter-tip assemblies is positioned such that the assemblies are parallel with the ground, the tips have a greater horizontal dimension than vertical dimension.
During operation of a dipper bucket a tip, particularly one mounted at the end of the lip, is subjected to loads from all directions. In an adapter-tip assembly the adapter functions to transfer the stress exerted on the tip to the dipper bucket. Consequently, an adapter must be able to resist stresses exerted on the tip from all directions.
In a previous tip and adapter assembly manufactured by the assignee of the instant invention, the nose of the adapter which was received in a complementary shaped socket formed in a tooth tip had a rectangular cross-section at its base which tapered to a small rectangular front edge. The rectagular front edge permitted the external shape at the front of the tip to have a spade-like shape. It was found that with this design the tip had a relatively high maximum stress with respect to a given load. Consequently, a relatively high percentage of metal was required in the rear of the tip compared to what could be put in the front of the tip.
Also, it was found that, during the casting of the tip, the sharp corners and fillets in the rectangular areas experienced thermal shock which resulted in quench cracks and other defects. Additionally, a proper fit between the tip and adapter was frequently hard to achieve from the parts as cast and machining of the adapter nose and tip socket was frequently required. In addition to the obvious expense resulting from machining the adapter and tip, the machining sometimes caused another problem in that the holes cast in the tip and adapter which receive a retaining pin were sometimes misaligned after machining. Further, the rectangular cross-section of the adapter tip interface caused higher maximum stresses in the corners than in the walls. Since the corners of the tip socket had to be thick enough to resist the maximum stress, the wall thickness was greater than necessary.
In some adapter-tip assemblies it is necessary for a workman to remove a pin which retains a tip on an adapter from the bottom of the assembly. This is difficult and inconvenient, especially when a tip must be replaced frequently. Another disadvantage of some pins is that they are a two- or three-piece assembly and the pieces are separable. This enables a workman to mix worn and unworn pieces to form an assembly, which is undesirable because the worn piece will cause the new pieces to wear faster than normal and/or the assembly will not properly retain the tip on the adapter. A further disadvantage of some multi-piece pin assemblies which include a resilient member which deforms when the pin is inserted or removed is that dust which collects around the pin assembly can prevent deformation of the resilient member and make pin removal difficult.
It is desirable to provide an adapter-tip assembly in which the adapter nose and the tip socket are shaped such that the maximum stress of the tip is equal in all directions and the percentage of metal which is provided in the spade section of the tip is maximized.
It is also desirable to provide an adapter-tip assembly in which sharp corners in the tip and adapter are eliminated so that the castings are easier to manufacture.
In addition, it is desirable to provide an adapter-tip assembly in which the tip can be mounted on the adapter as cast without further machining and the bores in the tip and adapter are properly aligned to receive a retaining pin.
Further, it is desirable to provide an adapter and tip having a pin assembly for retaining the tip on the adapter, which can be removed by a workman having access solely to the top of the assembly, which is unitary in that the pieces of the assembly are bonded together and which ensures that the resilient member can deform to permit easy removal of the pin assembly when dust is packed around the assembly.